

# -*- coding: utf-8 -*-

def binary_search(list,item):
  low = 0
  high = len(list) - 1
  
  while low<=high:
    mid = (low+high) / 2
    guess = list[mid]
    if guess == item:
      return mid
    if guess > item:
       high = mid -1
    else:
        low = mid + 1
  return None

  my_list = [1, 3, 5, 7, 9]
  print('hello')
  print binary_search(my_list, 3)
  print binary_search(my_list, -1)

